Iodine nutrition status and prevalence of abnormal TSH levels in schoolchildren aged 6-7 years in the autonomous community of the Basque Country

Introduction: An epidemiological study conducted between 1988 and 1992 showed iodine deficiency and endemic goiter in the schoolchildren of the autonomous community of the Basque Country.

Objectives: 1) To ascertain the iodine nutrition status of schoolchildren aged 6-7 years, and 2) to estimate the prevalence of abnormal TSH levels in capillary blood.

Population and methods: The study was conducted on 497 schoolchildren selected by random sampling. Median urinary iodine concentration (mUIC) was used to assess iodine nutritional status, and the reference interval derived from the study population was used to estimate the prevalence of abnormal TSH levels.

Results: The mUIC (P₂₅-P₇₅) was 140 (82-217) μg/L. A higher value was found in those who used iodized salt at home than in those who did not (146 [85-222] versus 126 μg/L [73-198], P<0.05). It was also higher in those who consumed 2 or more daily servings of milk and yogurt than in those taking less than 2 servings (146 [87-225] versus 110 μg/L [66-160], P<0.0001). Abnormal TSH levels were found in 2% of children. There was no correlation between TSH levels in capillary blood and urinary iodine concentrations (R=0.082; P=0.076).

Discussion and conclusions: Schoolchildren aged 6-7 years of the autonomous community of the Basque Country have an adequate iodine nutrition status. Use of iodized salt at home and daily consumption of milk and yogurt were associated to the highest UICs.